Agilent Technologies E1439 manual Synchronizing changes in multi-module systems

Using the Agilent E1439

Managing multiple modules

Synchronizing changes in multi-module systems

Multi-module systems require special treatment with respect to timing of frequency and filter changes. Center frequency changes may involve synchronizing the local oscillators of all modules in a system. Digital filter changes in multi-module systems require that the decimation counters be synchronized.

Calling the following functions voids synchronized multi-module setups:

age1439_clock_setup and related low-level clock setup functions age1439_clock_recover

age1439_input_autozero age1439_input_range_auto age1439_self_test age1439_state_recall

Special considerations apply to the measurement loop. See “The measurement loop in multi- module systems” on page 24.

Synchronous digital filter changes

In multi-module systems where synchronous sampling is required, the decimation counters in all the modules must be synchronous with each other. This condition can be forced by preparing each module in the system in advance. Any measurement in progress is terminated at this time and the module is placed in the Idle state. After each module is prepared, the next sync line transition causes the digital decimation counter to be reset and started at the same time. Once this is done, the decimation counters stay synchronized as long as the same ADC clock is used.

If you also intend to change the center frequency along with the digital filters, you should synchronize the digital filters first. Otherwise, the center frequency phase becomes unsynchronized when the digital filters are changed.

Synchronous center frequency changes

In multi-module systems you may prepare each module in advance of a frequency change, then perform the change synchronously by asserting the Sync line. This preserves the phase relationship of the local oscillators for all modules in the system. Certain special considerations apply to multi-module frequency changes:

•If all modules in a system are in the Idle state when the Sync line transition occurs, the LO frequency is updated and the next measurement is armed.

•If all modules are in the measurement state in continuous mode when the Sync line transition occurs, the LO frequency is synchronously updated, and the measurement continues.

•In continuous mode, care must be taken to assure that all modules are in the same state, either the Idle state or the Measure state, before the Sync line transition occurs, otherwise some modules re-arm while others continue the current measurement.

•In block mode, it is simplest to keep Forced Idle asserted during the Sync line transitions to keep all the modules in the Idle state.

•If you also intend to change the digital filters along with the center frequency, you should synchronize the digital filters first. Otherwise, the center frequency phase becomes non- synchronized when the digital filters are changed.

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